An electric power converter for converting DC power from a battery into AC power for driving a motor is mounted in an electric vehicle, a hybrid vehicle or the like.
The electric power converter has a plurality of semiconductor modules with built-in switching elements, and the semiconductor modules generate heat by a controlled current flowing through the switching elements.
In such an electric power converter, a laminated semiconductor unit is formed by alternately laminating the semiconductor modules and cooling pipes for cooling the semiconductor modules.
A pressing member for pressing the laminated semiconductor unit in a laminating direction is disposed at an end in the laminating direction of the laminated semiconductor unit, and these components are disposed in a frame.
Then, cooling efficiency is improved by making the semiconductor modules and the cooling pipes in close contact by an urging force of the pressing member.
Here, in terms of a coolability of the semiconductor module, and in terms of a rigidity of the laminated semiconductor unit, the urging force of the pressing member is required to be in a certain range.
However, the urging force of the pressing member depends on spring characteristics of the pressing member, an elastic deformation amount of the pressing member, or the like.
Further, the elastic deformation amount of the pressing member depends on dimensions of a case in the laminating direction, dimensions of the laminated semiconductor unit in the laminating direction, or the like.
Therefore, when design errors occur to them, an error occurs in the urging force of the pressing member as well.
In particular, since the dimensional errors of a plurality of semiconductor modules and the dimensional errors of a plurality of cooling pipes are accumulated, design errors tend to occur in the dimensions of the laminated semiconductor unit in the laminating direction, and in accordance with this, errors in the urging force of the pressing member tend to occur as well.
Therefore, an electric power converter disclosed in the Japanese Patent Application Laid-Open Publication No. 2013-146169 supports a pressing member by using cylindrical struts that are detachable with respect to a frame.
Then, by preparing a plurality of types of struts having various diameters, and by selecting appropriate struts among them in accordance with dimensions of a laminated semiconductor unit in a laminating direction, dimensional errors of the laminated semiconductor unit in the laminating direction are absorbed, and urging force of a pressing member is adjusted.
However, the electric power converter disclosed in the Publication No. '169 must provide the plurality of types of struts of different diameters as described above.
Therefore, there is a problem that it is difficult to improve the productivity of the electric power converter, and cost reduction is also difficult to achieve.